Remove SkBlitter:resetShaderContext()

Refactor SkDraw::drawVertices() to reset the whole blitter instead.

No noticeable bench diff.

  out/Release/nanobench --config 8888 -m patch_grid_colors_tex

Before:

   9/9   MB	1	9.24ms	11.4ms	11.5ms	15ms	16%	█▆▅▄▄▃▂▂▁▁	8888	patch_grid_colors_texs_big
   9/9   MB	1	5.2ms	5.2ms	5.2ms	5.21ms	0%	█▃▂▁▂▂▃▂▂▁	8888	patch_grid_colors_texs_medium
   9/9   MB	2	378µs	380µs	380µs	382µs	0%	█▆▅▄▄▁▄▄▆▄	8888	patch_grid_colors_texs_small

After:
   9/9   MB	1	9.29ms	11.5ms	11.6ms	15.3ms	17%	█▇▅▄▄▃▂▂▁▁	8888	patch_grid_colors_texs_big
   9/9   MB	1	5.15ms	5.16ms	5.16ms	5.18ms	0%	█▄▁▁▄▂▁▂▃▂	8888	patch_grid_colors_texs_medium
   9/9   MB	2	378µs	380µs	380µs	382µs	0%	█▅▄▃▁▄▄▄▃▄	8888	patch_grid_colors_texs_small

R=reed@google.com,mtklein@google.com,herb@google.com
BUG=skia:6168

Change-Id: I0b6b7d1297323681d8d2838040450c4e1afabc17
Reviewed-on: https://skia-review.googlesource.com/7626
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
4 files changed